Aquastyle DIY LED short circuit

If you have experience with diy LED's can you give me some advice on how to find a probable short?

40 Leds on 2 drivers (LPF-60D-48 one for the blue and the other for the white), each controlling 2 strings of 10. 4 fuses.

When I try it the 20 white work fine but one of the blue strings of 10 does not light.

Before turning it on (and after) I tested from wire to wire each Led-they still appear to be good. The tester is basically 2 AA batteries. I have an older multimeter that can test Amps, Volts, and contunuity but not many other bells and whistles. I switched the fuses around as well thinking it might be a bad fuse.

I have a picture of the led and heatsink, multimeter, and tester.

With what I have can I test for a short or do I need a better multimeter?

Many thanks....

 

are they soldered connectuons. Check for loose ir cold solder joints. Use a pencil with eraser on end. Use it to poke at each connection with power on. If you find one you will see it. Try this first. Troubleshooting 101.

 

Got it. The fuse holder they sent me was bad. One end wasn't passing current- but oddly enough they sent me an extra one to begin with (go figure). Threw me for a loop cause I suspected the fuse early on and tested for that. Well atleast I learned that my multimeter has a diode/continuity mode(s) that will light up an led. I was testing from led to led like you wouldn't believe.

Thanks